Long travel hydraulic cushion device



April 14, 1964 B. J. TRAUTMAN ETAL 3,128,884

LONG TRAVEL HYDRAULIC CUSHION DEVICE .5 Sheets-Sheet 1 Filed 00T.. 25, 1961 :LII im Aprl 14, 1964 B. .1. TRAUTMAN ETAL 3,128,884

LONG TRAVEL HYDRAULIC CUSHION DEVICE Filed Oct. 25, 1961 5 Sheets-Sheet 2 INVENTORS. BERNARD J'. TRAUTMAN WILLIAM R. SHAVER 7 EARL L. THOMPSON www iii-ia- April 14, 1964 B. .1. TRAUTMAN ETAL LONG TRAVEL HYDRAULIC CUSHION DEVICE '5 sheets-sheet s Filed Oct. 25, 1961 INVENTORS. BERNARD J'. TRAUTMAN WILUAM R. SHAVER United States Patent O 3,128,884 )LONG TRAVEL HYDRAULIC CUSHION DEVCE Bernard J. Trautman and Wiiiiam R. Shaver, Hammond, Ind., and Earl L. Thompson, Chicago, Ill., assignors to Iuiiman Incorporated, Chicago, Ill., a corporation of Delaware Fiied Get. 23, 1961, Ser. No. 146,769 14 Ciaims. (Ci. Z13-43) The present invention relates to hydraulic cushion devices and more particularly to an improved cushioning device of the type comprising basically two relatively telescoping components having arranged therebetween hydraulic fluid which is operative upon the application of a force on the components to dissipate the kinetic energy.

A cushioning device of the above type embodying the general principles is disclosed in U.S. Patent No. 3,003,- 436, of October l0, 1961, and U.S. patent application Serial No. 782,786, tiled December 24, 1958, now US. Patent No. 3,035,827, both assigned to the assignee of the present invention. These applications relate to a new and novel method and structure for providing a long travel cushioning arrangement achieving a substantially constant force-travel cushioning characteristic.

It is a principal object of the present invention to provide an improved long travel hydraulic cushioning device constructed and arranged to increase the endurance of the relatively slidable components against fatigue factors present in the device.

It is a further principal object to provide a long travel hydraulic cushioning device constructed and arranged in a manner to simplify the manufacture and reduce the cost thereof.

It is still a further object to provide a long travel hydraulic cushion constructed and arranged so as to reduce the galling effect between the various movable components thereof and thereby increase the trouble-free operating7 life of the device.

It is still another object to provide a new and novel arrangement for charging the hydraulic fluid into the device.

In the drawings:

FIG. 1 is a small scale cross-sectional view of the cushioning device embodying the present invention shown in its fully contracted position, and shown by the phantom lines in fully extended position;

FIG. 2 is a fragmentary cross-sectional enlarged view of the device in its fully contracted position as shown in FIG. 1;

FIG. 3 is a fragmentary cross-sectional enlarged view of the head of a metering pin embodying therein a check valve structure for charging hydraulic iiuid into the cushioning device;

FIG. 4 is a perspective view of the piston ring employed in the piston head;

FIG. 5 is a cross-sectional view taken substantially along the lines 5-5 of FIG. 2; and

FIG. 6 is an enlarged View of the key employed in FIG. 5 prior to being inserted in the keyways.

Referring now to FIGS. 1 and 2, there is shown a cushioning device It) embodying the present invention including generally a cylinder 11 having a bore 12 charged with a suitable hydraulic fluid; a uid displacement means 13 telescopingly arranged relative to the cylinder between a fully extended position as shown by the phantom lines of FIG. 1 to a contracted position upon the application of the shock force to the device and being operative upon the application of a shock to the unit to displace uid within the bore to dissipate the kinetic energy in the form of heat; a metering pin 14 for controlling the rate of displacement of the fluid within the bore to provide substantially constant force-travel cushioning characteristics to the device; and a resilient means 15 disposed between the fluid displacement means and the cylinder for returning the members to their fully extended position upon dissipation of the shock.

The cylinder 11 includes a tubular shell 16 formed preferably from a rigid metallic preformed tube capable of withstanding internal pressures without buckling, such as cold-drawn steel tubing of which the inner wall surface is suiiiciently smooth to permit eiiicient operation of the fluid displacement means 13 disposed therein. It has been found that the smoothness ordinarily obtained by the more or less conventional polished mandrel method of forming steel tubing is satisfactory. However, it is to be understood that a surface formed in any other manner having substantially the same smoothness characteristics may also be employed.

The shell 16 is closed at one end by a cylinder head 17 having a groove 17a formed therein for receiving the end of the tube and the latter is fixed therein as by welding to form a leak-proof joint. The cylinder head 17 is of somewhat larger diameter than the diameter of the shell 16 so as to provide a iiange engaging one end of the resilient spring-means 15 encompassing the cylinder.

A second cylinder head 18 is fixed within the bore 12 of the shell 1.6 between the ends thereof as by keying or any other suitable fastening means. A suitable keying structure is shown in FIG. 5 and includes three radially spaced keys 19 of the type shown in FIG. 6 which are each inserted into slots Z provided in the cylinder 11 and wedged into complementary keyway 21 formed in the cylinder head 13. For a more complete description of this type of keying arrangement, reference is made to copending U.S. application Serial No. 146,770, tiled concurrently herewith. For providing a seal between the inner surface of the tube 16 and the cylinder head l, there may be provided a sealing means such as an O-ring.

As shown the cylinder head I8 is formed with a hub Sil to which is attached one end of an invaginating tube 22 of which the function and structure will be more fully explained hereinafter. The cylinder head also includes a coaxial opening 23 for accommodating a piston rod 24 of the tiuid displacement device 13.

The huid displacement device 13 includes the piston rod 24 to one end of which there is connected a piston head 26 which is reciprocable within the bore between the cylinder heads 17 and 18 and to the other end of which there is connected a closure plate 27.

The piston rod 24 includes a bore 2S and may be formed of a rigid metallic material, such as cold-drawn steel tubing, and is provided adjacent the piston head 26 with a plurality of radially spaced ports 29 for providing communication between the cylinder bore 12 and the piston rod bore 28.

To minimize metal-to-metal Contact between the sliding components of the device in accordance with the present invention, the outer diameter of the piston rod 24 is substantially less than the diameter of the coaxial opening 23 in the cylinder Ihead 18 so as to provide an annular opening 31 between the outer wall of the tube and the inner wall of the opening 23. The annular opening 31 is sized to permit substantially free flow of hydraulic fluid to and from the invaginating tube 2.2 for purposes more fully to be explained hereinafter.

The piston head 26 is preferably formed from a metal such as steel and comprises a disc-like body having a planar Iforward face 32 and a planar rearward face 33. The planar rearward face -33 merges into a conical feed surface 34, which terminates in a rim 36 which denes the perimeter of an orice 37 formed coaxially in the piston head 26. The piston head 26 is formed on its forward face with a recess 38 which receives the terminal end of the tubular piston rod 24 and the latter is fixed to the piston head as by welding.

For guiding the fluid displacement means for relative telescoping movement within the cylinder 11 and for forming a seal between the inner wall of the cylinder and the piston head 26 in accordance with the present invention, piston head 26 is provided with an elevated seal forming guiding surface means 39. In this connection it is to be mentioned that the cushioning device is pri marily intended for use in a railway vehicle of the cushioned underfrarne type in which the cushioning de vice is mounted in a more or less conventional cushion pocket arranged between the underframe and a relatively movable superstructure. Under some circumstances the association of the cushion pocket with the underframe and superstructure is such that the fluid displacement means 13 and the cylinder 11 are axially misaligned or are subject to cooking.

Under these conditions, `during operation and in the presence of high unit pressures and high temperatures of the hydraulic uid in the device during the operation thereof, a sliding contact of the cylinder 11 and fluid displacement means creates many stresses within the unit. which tend to produce metal fatigue. Particularly troublesome is the problem of the sliding contact of the piston head 26 with the cylinder wall when the two are formed of materials having an ainity for each other and a misalignment occurs so that only an edge portion of the piston contacts the cylinder wall. This creates a stress somewhat in the nature of la clamping stress. ln the presence of this clamping like stress when metals having an affinity for each other are employed there results a galling or tearing of tiny metallic particles from the cylinder wall surface so as to roughen the same. Such roughening of the cylinder wall surface is undesirable, particularly because during the high velocity flow of the fluid normally associated with the operation of the cushioning device, excessive leakage results past the piston head 26 which affects the eiciency of the device in absorbing the shocks imparted thereto.

Primarily for the above reasons the guiding surface means 39 is formed from a material which does not have an affinity for the material of the cylinder wall because such materials are not as readily subject to galling the cylinder walls. Moreover, the guiding surface means must be capable of withstanding the high temperatures and the high pressures which are in the maximum range of about 8,000 p.s.i. without failure, for example, by deformation or fracture after prolonged use. As an additional factor the guide surface material must have a suiiiciently hard surface characteristic substantial to resist scoring.

A material found to be suitable for use with the long travel cushioning device of the present invention is a laminated phenolic resin such as `for example a type designated by the NEMA (National Electrical Manufacturers Association) as 9 Coarse, Grade C.

As shown in FIGS. 2 and 4, the `raised guiding surface means 39 formed of laminated phenolic resin, is constructed as a split expandable ring which is seated within a groove 41 formed on the periphery of the piston head 26. The ring -39 is constructed of greater thickness than the depth of the groove 41 and is snugly received within the groove 41 and expands and contacts the inner wall surface of the cylinder, thereby to form an eicient seal while at the same time providing a bearing surface which distributes the stresses associated with the telescoping movement of the piston head within the bore without the closure plate 27 which is formed preferably of a mild steel and includes a hub 42 and a ange 43 against which van end of' the resilient return spring means 15 abuts. The `hub 42 is of substantially the same diameter as the cylinder 11 and as shown in FIG. 2, the end of the latter abuts the hub 42 in the fully contracted position. The closure plate 27 is fastened to the piston rod 24 by way of a bolt 44 threaded into a plug 46 which is secured as by welding into the bore 28 adjacent the closure end thereof.

For metering the rate of flow from a high-pressure chamber 47 on one side of the piston through the orifice 37 of the piston head 26, the piston bore 28, and the ports 29 to the low-pressure chamber 48 on the opposite side of the piston 26, there is provided the metering pin 14. The metering pin 14 comprises essentially a rod of constant circular cross-sectional area along its length provided with a plurality of flutes 49, of which only one is shown, gradually tapering toward the rearward end thereof. The pin 14 is fixed at its head S0 as by threading into the cylinder head 17 of the cylinder 11. Upon relative movement between the cylinder and the fluid displacement means during the application of a shock to the unit, the piston head 26 is positioned relative to the metering pin 14 so that the flow through the orifice 37 and the flutes 49 of the metering pin at any given distance of travel imparts a substantially constant `force travel characteristic to the cushioning device. To this end, the flutes 49 are designed to conform substantially with the relationship 22 Aran/1-El wherein AX is the orice area of any position x, over the total nominal stroke d (length of surface in which the flutes are formed) and Ao is the initial orifice area defined by the orice and the llutes at the beginning of the stroke under conditions where a completely rigid body is being cushioned from compact. For a more complete description of the metering arrangement reference is made to the aforementioned U.S. patent applications Serial Nos. 782,726- and 856,963.

Fixed on and located forwardly of the ports 29 of the piston rod 24 is a stop ring 51 which, as shown in the phantom lines position of FIG. l, engages the open ended cylinder head 18 so as to limit the travel of the fluid displacement means 13 to its fully extended position. This provides a minimum low pressure volume in the chamber 48 for receiving the fluid from the chamber 48 via the orifice 37 and bore 2S of the piston rod 24.

For further extending the low-pressure volume, there is provided the invaginating tube or flexible fluid receiving member 22 which, as previously described, has one end thereof fixed to the hub 3) of the cylinder head 18 as by a hose clamp and an infolded end fixed to the piston rod 24 for movement therewith also by a hose clamp. The invaginating tube 22 is formed of a fluid impervious iiexible material which is capable of resisting corrosive effects of the hydraulic liquid employed in the unit and advantageously may be a neoprene-Buma type of rubber having special additives for low temperature flexibility.

As shown the resilient means 15 includes three helical compression springs 15a, 15b and 15e which are arranged in tandem and employed for the purpose of extending the device to its fully extended position after the shock has been dissipated. The compression springs may be formed of a heat treated spring steel. If desired the resilient means 15 may be in the form of either single or dual springs.

For the purpose of reducing the overall cross-sectional area of the unit in accordance with the present invention, a charging check valve device 52 for charging hydraulic uid into the unit is incorporated into the head 563 of metering pin 14, as shown in FIG. 3. The head 50 of the metering pin 14 is provided with an inner axial recess 53 which communicates with an enlarged recess 54 opening at the terminal end of the head. Threadably secured within the inner recess 53 is a plug S6 provided With a straight through bore 57 of which the outer portion is formed to receive an Allen-type wrench for setting the plug in position. The bore 57 communicates with an axial passage 58 which communicates with a transverse diametrical passageway S9 formed in the body portion of the metering pin and located so as to be in constant communication with the bore of the cylinder when the metering pin 14 is assembled on the cylinder head 17. Disposed within the recess 53 is the check valve device 52 including a ball 61 biased by way of a compression spring 62 into seating engagement over the plug passageway 57. For precluding leakage through the check valve structure, the enlarged recess 54 of the metering pin head has screw-threaded therein a sealing plug which is preferably in the form of an Allen-type pipe plug 63.

Assuming the device is assembled and devoid of hydraulic fluid and in its fully extended position as shown by the phantom lines of FIG. l and the plug 63 is removed from the head 59 of the metering pin 14 to charge the device, hydraulic fluid, such as a non-corrosive, highviscosity oil which retains its viscosity over a relatively Wide range of temperatures is introduced in the passage 57 whereupon the flow of hydraulic fluid unseats the ball 61 to supply hydraulic fiuid via the recess 53, passage 58, and diametrical passageway 59 into the high-pressure chamber 47 of the bore. At the same time hydraulic liuid flows through the orifice 37 in the piston head 26 and the utes 49 of the metering pin 13, the piston bore 28, and ports 29 to the low-pressure chamber and via the annular passageway 31 into the invaginating tube. The device is charged so that a pressure exerted by the hydraulic fluid in the fully extended position is maintained at a minimum say, for example, about 2 p.s.i.

Assuming further that the cushioning device 10 is employed in a railway car having a superstructure mounted for movement relative to the underframe wherein the device is mounted in pocket-like structures to isolate the shock from the superstructure during normal transit and in the absence of buff or draft forces, the cushioning device is in the fully extended position shown in FIG. 1 with the stop ring 51 contacting the cylinder head 15. Upon the application of a shock in either buff or draft to the underframe, the tubular cylinder 11 and the piston head 26 and cylinder head 17 start movement toward each other. As the cushioning device contracts under the force being cushioned, the metering pin 14 displaces hydraulic fluid contained within the bore 28, piston rod 24, and the high-pressure chamber 47 on one side of the piston head causing a hydraulic iiuid flow through the orifice 37 into which the metering pin extends. Such hydraulic iiow through the orifice 37 is determined by its position relative to the flutes 49 which are designed to provide a substantially constant force travel characteristic as the hydraulic cushion contracts under the shock force imposed upon the latter. In other words the flutes 49 of the metering pin are cooperative with the orifice 37 so that the flow of hydraulic fluid therethrough for every unit of travel of the piston head relative to the cylinder 11 imparts a substantially constant cushioning effect to the cushioning device.

The hydraulic flow initiated by the relative movement of the piston head Z6 and the cylinder 11 flows from the high-pressure chamber 47 through the orifice and into the bore 28 of the tubular piston rod 24 and thence radially outward through the ports 29 to the low-pressure chamber 48 of the bore 12. The hydraulic fluid flow through the ports 29 occurs at a relatively high velocity so that a turbulence is created as the displaced fluid enters the lowpressure chamber. This turbulence is caused at least in part by the radially directed flow of hydraulic fluid impinging directly against the inner wall of the tube soy that a major portion of the kinetic energy of the hydraulic fluid is dissipated in the form of heat. In this connection it is to be noted that the stop ring 51 contacting the cylinder head 15 is effective to limit the volume of the low-pressure chamber 48 and in this manner provides a chamber into which the hydraulic iluid displaced by the piston may freely enter as described above and thereby dissipate the kinetic energy in the form of heat under minimum shock or load conditions.

Upon further contraction of the cushioning device, the high-pressure chamber continues to reduce in volume because of the advancement of the piston head 26 toward the cylinder head 17. The hydraulic fluid passing through the orifice 26 fills the low-pressure chamber 48, while at the same time a volume of hydraulic fluid equivalent to that displaced by the total entry into the chamber 48 of the piston passes through the annular opening 31 of the cylinder head and into the pocket defined by the invaginating boot 22 which inflates or expands and assumes substantially the position shown in the full line position of FIG. 2. The relationship of the diameter of the piston rod and the opening in the cylinder head 18 is such as to provide a relatively large volume annular opening primarily for the purpose of accommodating any relative cocking of the piston rod and cylinder head to avoid any engagement therebetween, as well as to establish a lowpressure hydraulic liquid ow between the low-pressure chamber and the invaginating boot.

After the shock has been fully dissipated the compression springs 15a, 15b and 15e acting in tandem are operative to return the hydraulic cushion components to the initial extended position. During this movement, under the action of the compression springs, the oil ow previously described is reversed and the invaginating tubular member detlates and returns to the position shown, thereby insuring that the hydraulic liquid displaced by the piston is restored to its normal operative position.

What is claimed is:

1. A hydraulic cushioning device comprising a fluid containing cylinder having a closed end and an open end, fluid displacement means received in said cylinder and including a piston head having guiding surface means elevated above the peripheral surface of said head contacting the inner wall of said cylinder to guide said uid displacement means for reciprocation relative to said cylinder and to provide a seal so as to define a high-pressure charnber adjacent said closed end of said cylinder and a lowpressure chamber adjacent said open end, orifice means formed in said fluid displacement means to provide communication between said high and low-pressure chambers, a piston rod connected to said piston head, and which extends through said open end, and a flexible expandable liuid receptacle attached to said cylinder and said piston rod to close said open end.

2. A hydraulic cushioning device comprising a uid containing cylinder having a closed end and an open end, fluid displacement means received in said cylinder and including a piston head having guiding surface means formed from a material which does not have an affinity for the material from which said cylinder is formed, said guiding surface means being elevated above the peripheral surface of said head and contacting the inner wall of said cylinder to guide said fluid displacement means for reciprocation relative to said cylinder and to provide a seal so as to define a high-pressure chamber adjacent said closed end of said cylinder and a low-pressure chamber adjacent said open end, orifice meansformed in said fluid displacement means to provide communication between said high and low-pressure chambers, a piston rod connected to said piston head and which extends through said open end to define an annular passage therein and within said cylinder, and a uid receptacle attached to said cylinder and said piston rod and in constant communication.

3. A hydraulic cushioning device comprising a fluid containing cylinder having a closed end and an open end,

fluid displacement means received in said cylinder and including a piston head having guiding surface means formed from a laminated phenolic resin, said guiding surface means being elevated above the peripheral surface of said head and contacting the inner wall of said cylinder to guide said uid displacement means for reciprocation relative to said cylinder and to provide a seal so as to define a high-pressure chamber adjacent said closed end of said cylinder and a low-pressure chamber adjacent said open end, opening means formed in said fluid displacement means to provide communication between said high and low-pressure chambers, a piston rod connected to said piston head and which extends through said open end to define an annular passage therein and within said cylinder, a flexible expandable fluid receptacle operatively connected to said cylinder and said piston rod and in constant communication with said annular passage, and metering means disposed in said cylinder and coacting with said liuid displacement means for maintaining the flow of said fluid from said high-pressure chamber to said low-pressure chamber through said opening means at a rate imparting substantially constant force travel characteristics to said device upon shock impact thereto.

4. The invention as defined in claim 3 in which said piston head is provided with a groove, and said guiding surface means is in the form of a split ring seated in closed condition in said groove and projects substantially outwardly therefrom.

5. A hydraulic cushioning device comprising a fluid containing cylinder including a shell having a closed cylinder head at one end thereof and an open cylinder head spaced from the other end of said cylinder and said closed cylinder head, fluid displacement means received in said cylinder and including a piston head located between said cylinder heads and having resinous guiding surface means elevated above the perpheral surface of said piston head contacting with the inner wall of said cylinder to guide said fluid displacement means for reciprocation relative to said cylinder and to provide a seal so as to define a high-pressure chamber adjacent said closed cylinder head and a low-pressure chamber adjacent said open cylinder head, orifice means formed in said fluid displacement means to provide communication between said high and low-pressure chambers, a piston rod connected to said piston head and which extends through siad open cylinder head, said piston rod and said open cylinder head establishing a clearance therebetween to permit non-engaging cocking of said piston rod relative to said open cylinder head, and a flexible expandable fluid receptacle attached to said open cylinder head and said piston rod to close the other end of said cylinder.

6. The invention as defined in claim 5 in which said guiding surface means is formed from a laminated phenolic resin.

7. The invention as defined in claim 5 in which said piston head is provided with a peripheral groove, and said guiding surface means is formed from a laminated phenolic resin in the form of a ring seated in said groove but of suliicient thickness to project substantially therefrom.

8. A hydraulic cushioning device comprising a cylinder having a closed end and an open end, fluid displacement means received in said cylinder and including a piston head having a guiding surface means elevated above the outer surface of said piston head and contacting the inner wall of said cylinder to guide said fluid displacement means for reciprocation relative to said cylinder and to provide a seal so as to define a high-pressure chamber adjacent said closed end of said cylinder and a lowpressure chamber adjacent the open end thereof, openings formed in said fluid displacement means including an axial orifice formed in said piston head to provide communication between said high-pressure chamber and said low-pressure chamber, a piston rod connected at one end to said piston head and extending through the open end of said cylinder to define an annular passage therein and within said cylinder, a flexible expandable fluid receptacle attached to said cylinder and said piston rod and in constant communication with said annular passage, a metering pin fixed to said closed end of said cylinder and extending through said axial orifice in said piston head to control the rate of flow from said high-pressure chamber to said low-pressure chamber upon the application of a force to said device to impart substantially constant force travel characteristics thereto, said metering pin including fluid charging passageways communicating with said cylinder, and a one-way check valve device disposed in said passageways to permit charging fluid into said cylinder.

9. A hydraulic cushioning device comprising a cylinder having a closed end defined by a first cylinder head and an open end defined by a second cylinder head having an axial opening, fluid displacement means received in said cylinder and including a piston head having a resinous guiding surface means elevated above the outer surface cf said piston head and contacting the inner wall of said cylinder to guide said fluid displacement means for reciprocation relative to said cylinder and to provide a seal so as to define a high-pressure chamber adjacent said closed end of said cylinder and a low-pressure chamber adjacent the open end thereof, openings formed in said fluid displacement means including an axial orifice formed in said piston head to provide communication between said high-pressure chamber and said low-pressure chamber, a piston rod connected at one end to said piston head and extending through said axial opening 0f said second cylinder head with substantial radial clearance therebetween, a flexible expandable fluid receptacle attached to said second cylinder head and said piston rod, a metering pin fixed to said first cylinder head and extending through said axial orifice in said piston head to control the rate of flow from said high-pressure chamber to said low-pressure chamber upon the application of a force to said device to impart substantially constant force travel characteristics thereto, said metering pin including fluid charging passageways communicating with said cylinder, and a oneway check valve device disposed in said passageways to permit charging fluid into said cylinder.

10. A hydraulic cushioning device comprising a cylinder having a pair of spaced cylinder heads, fluid displacement means received in said cylinder and including a piston head contacting with the inner wall of said cylinder to guide said fluid displacement means for reciprocation relative to said cylinder and to provide a seal so as to define a high-pressure chamber adjacent one of said cylinder heads and a low-pressure chamber adjacent the other of said cylinder heads, openings formed in said fluid displacement means including an axial orifice formed in said piston head to provide communication between said high-pressure chamber and said low-pressure chamber, a piston rod connected at one end to said piston head and extending through the other of said cylinder heads, a flexible expandable fluid receptacle attached to said other cylinder head and to said piston rod, means providing a substantially constant communication between said low-pressure charnber and said fluid receptacle, a metering pin fixed at one end to said one cylinder head accessible from the exterior of said one cylinder head and extending through said axial orifice in said piston head to control the rate of flow from said high-pressure chamber to said low-pressure chamber upon the application of a force to said device to impart substantially constant force travel characteristics thereto, said metering pin including fluid charging passageways adjacent said fixed end communicating with said highpressure chamber of said cylinder, and a one-Way check valve device disposed therein to permit charging uid into said cylinder.

11. The invention as defined in claim 9 wherein a first of said fluid charging passageways includes said check valve therein and extends axially of said metering pin and is accessible externally of said cushioning device at one end thereof, the remaining end of said first pasageway being in 9 communication with a second passageway extending transversely through said metering pin.

12. The invention as defined in claim 10 wherein a first of said fluid charging passageways includes said check valve therein and extends axially of said metering pin and is accessible externally of said cushioning device at one end thereof, the remaining end of said first passageway being in communication with a second passageway extending transversely through said metering pin.

13. In a hydraulic cushioning device wherein a cylinder is provided with an intermediate cylinder head internally thereof through which piston rod means is reciprocable within said cylinder and a piston head in sliding sealing engagement with said cylinder is reciprocable therein relative to said cylinder head, the improvement comprising an outer peripheral seal band carried by said piston head and in sliding sealing engagement with said cylinder, said seal band being formed from resinous material and projecting from the outer periphery of said piston head to permit cocking of said piston head relative to the longitudinal axis of said cylinder without contact between said piston head and cylinder surface except by means of said band, said cylinder head including a bore through which said piston means reciprocates, which bore is of substantially greater diameter than that of said piston means to accommodate cocking of said piston means therein without accompanying contact therebetween.

14. In a hydraulic cushioning device wherein a cylinder is provided with piston means reciprocable therein and a metering pin carried by a cylinder head which projects through the head of said piston means to meter the tloW of uid past said piston means, a provision of fluid charging means carried by said metering pin and cylinder head, said charging means comprising passage means in said metering pin which at one end is in communication with the interior of said cylinder and which at another end is accessible externally of said cylinder through said cylinder head, and check valve means in said passage means between the ends thereof to permit uid charging of said cylinder and to prevent iluid leakage therefrom through said passage means.

Zanow et al May 8, 1962 Peterson May 22, 1962 

1. A HYDRAULIC CUSHIONING DEVICE COMPRISING A FLUID CONTAINING CYLINDER HAVING A CLOSED END AND AN OPEN END, FLUID DISPLACEMENT MEANS RECEIVED IN SAID CYLINDER AND INCLUDING A PISTON HEAD HAVING GUIDING SURFACE MEANS ELEVATED ABOVE THE PERIPHERAL SURFACE OF SAID HEAD CONTACTING THE INNER WALL OF SAID CYLINDER TO GUIDE SAID FLUID DISPLACEMENT MEANS FOR RECIPROCATION RELATIVE TO SAID CYLINDER AND TO PROVIDE A SEAL SO AS TO DEFINE A HIGH-PRESSURE CHAMBER ADJACENT SAID CLOSED END OF SAID CYLINDER AND A LOWPRESSURE CHAMBER ADJACENT SAID OPEN END, ORIFICE MEANS FORMED IN SAID FLUID DISPLACEMENT MEANS TO PROVIDE COMMUNICATION BETWEEN SAID HIGH AND LOW-PRESSURE CHAMBERS, A PISTON ROD CONNECTED TO SAID PISTON HEAD, AND WHICH EXTENDS THROUGH SAID OPEN END, AND A FLEXIBLE EXPANDABLE FLUID RECEPTACLE ATTACHED TO SAID CYLINDER AND SAID PISTON ROD TO CLOSE SAID OPEN END. 